This invention relates to an improved one bath dyeing process for the dyeing of cellulosic containing materials with fiber reactive dyestuffs including blends of polyester/cellulosic materials with disperse and fiber reactive dyestuffs.
Numerous processes have heretofore been utilized for the dyeing of textile materials such as yarns, fabrics and nonwovens with wide divergence among the process parameters, depending upon the particular material being dyed, and/or the particular type of dyestuff being employed. Of particular importance are processes that have been utilized to dye textile materials that are constituted from different types of raw materials, exemplified by polyester-cotton blends. With such blends, where the cellulosic ingredient is hydrophilic in nature and the polyester component is oleophilic in nature, different colorant systems are required for dyeing the two components. Specifically, different classes of dyestuffs are necessary for the proper dyeing of cellulosic materials than for the proper dyeing of polyester materials with attendant variance in dyeing process conditions. Conventionally, dyers utilize a two bath system for dyeing polyester-cotton blends in which the polyester component is first dyed in a bath containing disperse dyestuffs, after which the textile material is rinsed, the dyestuff cleared, and the cotton component thereafter dyed in a subsequent bath containing fiber reactive colorants. Subsequent to the separate dyeing of the two components, the material is rinsed and subjected to further normal processing steps. Such a two bath procedure is in widespread use today, even though certain further dyeing techniques have been developed as alluded to hereinafter.
In utilizing the conventional two bath process, not only is the dyeing operation expensive and time consuming, but the process is particularly energy intensive. With different baths, substantial energy is expended for raising the bath temperature from ambient to elevated temperature conditions at several intervals during the process. Moreover, large amounts of dyestuffs and auxiliaries are needed to achieve desired yields, considerable rework is necessary due to shade variability and unlevel dyeings due to strike rate of reactives, and the protracted length of time required to complete dyeing by the two bath process reduces the production capacity of the dyeing equipment.
Presently, the availability of energy adequate to run energy intensive commercial processes, including dyeing operations is of major concern, not to mention the vastly increased cost of same. Consequently mush effort has been devoted to improving commercial processes, including dyeing, attempting to reduce energy requirements necessary for the dyeing of all materials, particularly polyester-cotton blends which are notoriously expensive and time consuming using state of art techniques. One relatively new process for dyeing polyester-cotton blends involves the addition of disperse and reactive dyestuffs capable of dyeing both the polyester and the cotton, along with necessary auxiliaries, into a single dye vat where the polyester component of the material is first dyed under acidic conditions. Thereafter temperature of the dye bath is reduced and electrolyte and alkali are added to the bath to raise the pH and salt content for dyeing of the cellulosic component with the already present fiber reactive dyestuffs. This particular one bath, two stage process, though representing improvement over the conventional two bath process, is very limited as to dyestuffs that may be employed therein, and does not represent a truly significant improvement over the two bath process insofar as energy requirements are concerned. Particularly, a very limited selection of fiber reactive dyestuffs may be used in the particular process, commonly referred to as the "hot dyers".
A further process that has been developed, attempting to improve economics of the dyeing of textile materials constituted from cellulosic and non-cellulosic blends is referred to as RID (Rapid Inverse Dyeing). The rapid inverse dyeing process is particularly directed to the dyeing of polyester-cotton blends. In this process, the cotton component is dyed first with fiber reactive dyestuffs after which the bath is dropped, the material rinsed, and a second bath is prepared with disperse dyestuffs in which the polyester is then dyed. Rapid inverse dyeing requires a shorter dye cycle, and is less energy intensive than either the conventional two bath system or the one bath, two stage system, both of which are set forth above.
The present invention represents an improvement over all of the prior art processes discussed above. A true one bath dyeing system is provided, the parameters of which permit successful dyeing of 100% cellullosic materials and polyester-cellulosic blends. Blends may be dyed with disperse and fiber reactive dyestuffs, while the 100% cellulosic material is dyed with fiber reactive dyes. While there is wide general variation in preferred dyeing techniques for the various subgroups of fiber reactive dyestuffs (identified hereinafter), with very minor exception, known fiber reactive dyestuffs may be employed in the present process with some slight variation in process parameters, the result of which enables one to achieve particularly level dyeing, excellent yield and good dye fastness. In fact, the present process permits uniform dyeing with certain shades that heretofore has been very difficult to dye by the conventional two bath process, except with substantial reworking, and even then poor wet fastness was present.
In general, the one bath process according to teachings of the present invention is neither taught nor suggested by the known prior art, and has the following attendant advantages: (a) reduced dye cycle time, and thus greater productivity from the dyeing equipment; (b) decreased labor cost/overhead due to increased production; (c) substantial reduction in the energy utilized; (d) increased yield for many fiber reactive dyes, especially when dyeing selected dark or heavy shades; (e) less time involved for dye add cycles, if needed; (f) more level dyeing; and (g) less dyestuff required in most cases.